Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with agraphical user interface showing the new design.

The outermost broken line rectangle illustrates a display screen orportion thereof and forms no part of the claimed design. The remainingbroken lines illustrate portions of the graphical user interface thatform no part of the claimed design.

CLAIM I claim the ornamental design for a display screen or portionthereof with a graphical user interface, as shown and described.